Prior Art
Prior art systems such as that shown in U.S. Pat. No. 4,484,543, entitled "Adjustable Non-throttling Control Apparatus For Spark Ignition Internal Combustion Engines" illustrate the changing of the belt length from two shafts. Along the belt path is a pair of idler wheels, wherein one wheel is moved by an external mechanism, such as a throttle of an engine, and the other wheel is moved under the force of a spring. In this system, a constant level of tension in the belt is not maintained.
U.S. Pat. No. 4,438,737, entitled "Apparatus and Method For Controlling The Valve Operation of an Internal Combustion Engine" illustrates a pair of idler arms controlling the path of a timing belt from the crankshaft to the camshaft. The upper idler arm is controlled by an electric motor which changes the length of a rod to pivot the upper idler arm. The lower idler arm follows the belt. The tension level in the belt is not maintained.
U.S. Pat. No. 4,530,318, entitled "Intake and Exhaust Valve System For Internal Combustion Engine" illustrates a means for moving the position of a controlled idler pulley between two driven pulleys to change the relative position of each of the driven pulleys relative to each other. A pair of idler pulleys is adjusted by the belt as the controlled idler pulley is repositioned. The tension level in the belt is not maintained.
U.S. Pat. No. 3,986,484, entitled "Camshaft for Controlling Variably Opening Valves" illustrates a linkage means for axially moving a camshaft while at the same time transversely moving a pair of idler wheels on the belt between a crankshaft and a pair of camshafts. The idler rollers are in a rigid spatial relationship on either side of one of the camshafts. As the camshafts are axially moved, the angular relationship between the two camshafts is altered. In this system the tension level in the belt is not maintained since both idler rollers move the same amount.
In all of the above systems, the tension level in the belts or chains being variable will provide inaccurate timing during each engine operation and harmfull stresses on the belts or chains.